Suggest to modify the layout of the debug buttons

[sj-raima]

I would suggest to lay out these buttons in a more intuitive way. In general all the buttons for reverse operations should be to the left and all buttons for forward operations should be to the right.

Also, all the up and down arrows should be slightly tilted to indicate the direction.

In the case we are doing rr I suggest we have these buttons first:

"Reverse Finish", "Reverse Into", "Reverse Over", "Reverse", "Set Checkpoint"

Followed by these buttons:

"Continue", "Step Over", "Step Into", "Restart", "Disconnect"

Observe that the order of the reverse operations are reversed compared to the forward counterparts. This makes for an intuitive placement with the illusion of a mirror in the middle. "Set Checkpoint" could instead be placed furthest to the left or to the right.

See also issue #184